Convert typedef'd ENUMs to use NS_ENUM() macro

This has plenty of benefits, including better code completion and error
checking than other methods.
Merge https://github.com/SlaunchaMan/FCModel
Rewrote instance uniqueness to be much simpler since FCModelCache no longer performed actual caching (that was old, unreleased behavior).
Added podspec, I think. It's my first time, be gentle
Workspace gitignore fixes for Cocoapods